Hi Bill,
1 – Emergency blanket
Reflective space blanket… take it or leave it. What do you guys think?
The first post I ever made to this forum dealt with an
emergency shelter tarp/blanket comparison test I conducted one chilly evening. I later conducted another, but realize now I forgot to post about it; an oversight I hope to correct soon.
Of least importance was insulation:
Essentially, I found the type of material mattered little; ripstop nylon tarp, plastic bag, tyvek sheet or whatever. What mattered much more was the thickness of the material. Thicker was better, but only so much.
Of moderate importance was convection:
All of the materials I tested were basically nonporous. Tyvek is porous and my ripstop tarps were perforated where sewn, of course. But they all blocked light breeze and convection heat-loss fairly well. If the material was closed on three sides to form a bag it made a significant difference. Bags were warmer than sheets, since they were automatically sealed against air leakage on most sides.
Of greatest importance was
reflection:
What was overwhelmingly obvious during both my tests was that any of these materials became two to three times warmer if it was aluminized! I have an aluminized emergency sleeping bag that I think is made of tyvek. I've also gotten "Space" blankets and bags, and one aluminized ripstop nylon tarp.
The Land/Shark is a nice thick ripstop bag. The 6mil International Distress Orange survival bag I got from Blueline Outfitters is a very nice thick plastic bag. Either was worlds above the yellow TMRU Tube Tent or a trash bag ... even the 4mil ones I found. None of these items compared to even the flimsiest of aluminized sheets! ("Flimsy" is an important word, though. The mylar sheets and bags are not sturdy at all! This drawback made me test the Space Bag inside some of the more durable bags, which were all then VERY warm!)
Some people quote tests that show "Space" blankets don't insulate any better than a plastic sheet. I'm not a physicist, but I know the difference between insulation and reflection. So what if they don't insulate? They're not supposed to! They're supposed to reflect body heat, and they work nicely ... so nicely that I would find myself becoming
too warm during my test, and open the bag or blanket to allow a little more convection to cool me down a bit ... something I was too chilly to want to do with any of the other items in the test.
So I'd say hold onto the survival blanket. It's small anyway. (Or, trade it for a bag when you get a chance.)
Stay safe,
J.T.